Drag figures for Kamm cut teardrops at various lengths?

[aerohead]

Walter Lay's 1933, 4-configuration half-body model showed a range from Cd 0.30, to Cd 0.12, depending on tail length.
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In 1934, Carl Breer, of Chrysler Corporation modified a DeSoto Airflow test mule.
* Reshaping the car's tail, from a ducktail to a Koenig-Kamm chopped-tail lowered the drag from Cd 0.51, to Cd 0.268.
* By adding a stinger, creating a full boat-tail they measured Cd 0.244.
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The circa-1935, FKFS Koenig-Kamm, 7-configuration, 1/2-body test model returned a range of Cd 0.258, to Cd 0.20, depending on tail length.
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Allegedly, there was a Cd 0.18, 'long-tail' variant of the 1946 Mathis V333, by Aerodynamicist, Jean Andreau.
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Porsche began running 'long-tail' variants at Le Mans, beginning around 1967, designed specifically for the Mulsanne Straight.
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Robert Cumberford was party to the 1973 design of a Cd 0.203 'city car', which, when fitted with a 72" boat-tail dropped to Cd 0.16.
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Daimler-Benz, Mercedes-Benz, 1978, C-111 III record car came in three flavors:
Cd 0.237
Cd 0.195
Cd 0.178
depending on length of boat-tail. Setting a closed-course land speed record.
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In 1980, ITworks Volkswagen transporter received a push, from 27-mpg, to 34-mpg, thanks in part to a truncated boat-tail.
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Around 1981, NASA published results for their Ford E-100 Econoline modifications.
* Adding the truncated boat-tail reduced the van from Cd 0.347, to Cd 0.242.
* Adding their stinger only dropped the Cd to 0.238 ( this tail extension was embedded within turbulence ).
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Rolf Buchheim, of Volkswagen tested a short and long-tail 1981, VW Flow-Body, half-body, Cd 0.15 vs Cd 0.14 for the 'long-tail'.
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GM's 1982 Cd 0.23 Aero 2000, got stretched into the Cd 0.14 Aero 2002.
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General Motors used a 'long-tail' variant of their 1987, OLDSMOBILE AEROTECH record car for the long course at the Firestone Proving Grounds, Ft. Stockton, Texas, setting a closed-course land speed record.
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In 1990, ITworks' 'Spindletop' Honda CRX streamliner set a USFRA speed record at Bonneville. The boat-tail proved to provide the largest speed increase.
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Leaving Bonneville, Spindletop indicated it's highest mpgs, recorded to date at the time. Low 60s mpg at the old double-nickel speed limit.
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GM returned to Ft. Stockton in 1993, with a long-tailed GM Impact/ EV1, Cd 0.137 vs Cd 0.197, and set a closed-course land speed record for an electric car, at over 183-mph ( 100 + mpg equivalent, if combustion powered)
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You may have seen the 2005 AeroCivic.
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In 2014, the boat-tailed Spirit of Ecomodder indicated 6.3% lower drag than the 2013 Prius, tested at the same time at DARKO.
Using the Prius as a calibration model ( tested @ DARKO, A2 Wind Tunnel, and Toyota ) SPIRIT indicated for Cd 0.243 @ A2, and Cd 0.234 @ Toyota.
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At the 2014 USFRA World of Speed, at Bonneville Int'l Speedway, the boat-tail helped add 9-mph to SPIRIT's top speed.
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The 2016 Mercedes-Benz IAA concept indicates for a drag reduction with it's extensible tail section ( Cd 0.19 ).
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And Mercedes-Benz 2022, EQXX concept also sports an active body elongation, helping with a Cd 0.1716.
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For a generic SUV, a boat-tail generates a delta-Cd 0.085 drag reduction ( 23.9% ), Ph.D. Joseph Katz, Professor, Aerospace Engineering, San Diego State University, MECHANIX ILLUSTRATED, March, 2017.
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' the drag reduction from an elongated tail varies almost linearly with the reduction in cross section area.' Jeff Howell et al.,' Streamlined Tails-The Effects of Truncation on Aerodynamic Drag,', Loughborough University, Abstract, SAE Paper 2020-01-0673